The Jejunum and Ileum Mediate Increased Calcium Absorption for Bone Mineralization During Postnatal Development via TRPV6 and Cav1.3 (OR26-07-19)

Abstract Objectives Intestinal Ca2+ absorption early in life is vital to achieving optimal bone mineralization. The molecular details of intestinal Ca2+ absorption have been defined in adults, after peak bone mass has been reached, but are largely unexplored during development. We sought to delineate the molecular details of transcellular Ca2+ absorption across the small intestine which facilitate a positive calcium balance during growth. Methods We used wildtype, Cav1.3 knockout and Trpv6 mutant mice. Expression of small intestinal and renal calcium transport genes was assessed using quantitative PCR. Net transcellular 45-calcium flux across intestinal segments was measured in Ussing chambers. Femurs we analyzed using micro-CT and histology. Results Significant TRPV6 mediated Ca2+ flux across the duodenum was absent in pre-weaned (P14) mice but occurred post-weaning. In contrast, we found significant transcellular Ca2+ absorption in the jejunum and ileum at P14 but not 2 months. TRPV6 and Cav1.3 are necessary for this jejunal absorption and Cav1.3 appears to mediate absorption across the ileum although compensation is present in knockout pups. Knockout of Cav1.3 induces a compensatory increase in renal Ca2+ reabsorption in P14 mice although these pups have increased growth plate thickness suggesting delayed bone mineralization. Conclusions This work provides molecular details of how the small intestine facilitates increased demand for Ca2+ early in life to meet the requirements of growth and highlights the complexity of the multiple mechanisms involved in achieving a positive Ca2+ balance. Funding Sources This work is funded by grants from the Women and Children's Health Research Institute, supported by the Stollery Children's Hospital Foundation, and the National Sciences and Engineering Research Council to RTA, who is the Canada Research Chair in Renal Epithelial Transport Physiology. MRB is supported by a Vanier Canada Graduate Scholarship, Alberta Innovates Clinician Fellowship and an NSERC Michael Smith Foreign Study Supplement. H. Dimke is funded by the Danish Medical Research Council. Work at UdS was funded by Deutsche Forschungsgemeinschaft (DFG) by IRTG1830 (to JE, VF), Sonderforschungsbereich (SFB) 894 (to JE, PW) and SFB TRR152 (to VF).

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Ingestion of the soluble dietary fibre, polydextrose, increases calcium absorption and bone mineralization in normal and total-gastrectomized rats

British Journal Of Nutrition ◽

10.1017/s0007114500001999 ◽

2000 ◽

Vol 84 (5) ◽

pp. 655-661 ◽

Cited By ~ 25

Author(s):

Hiroshi Hara ◽

Takuya Suzuki ◽

Yoritaka Aoyama

Keyword(s):

Small Intestine ◽

Dietary Fibre ◽

Short Chain Fatty Acid ◽

Guar Gum ◽

Calcium Absorption ◽

Bone Mineralization ◽

Water Soluble ◽

Soluble Fibre ◽

Soluble Dietary Fibre

We previously demonstrated that feeding a highly fermentable and water-soluble dietary fibre, guar-gum hydrolysate (GGH) increased intestinal absorption of insoluble Ca salts in total-gastrectomized rats. In the present study, we examined the effects of feeding a less fermentable and water-soluble fibre, polydextrose (PD), on Ca absorption and bone mineralization in the normal and total-gastrectomized rats in comparison with the effects of GGH. Apparent Ca absorption was severely lowered by gastrectomy, and PD feeding (50 g/kg diet) partially restored the reduction of Ca absorption similarly to GGH feeding (50 g/kg diet). PD feeding also increased the Ca absorption in normal rats, but not GGH feeding. Femur Ca concentration was reduced with gastrectomy. Feeding PD for 21 d increased the bone Ca concentration in both normal and gastrectomized rats, but GGH feeding did not. In rats fed PD, pH of the caecal contents was lower than in rats fed fibre-free and GGH diets; however, soluble Ca concentration in the caecal contents was not different between the diet groups. Short-chain fatty acid concentrations were much lower in the PD groups than in the GGH groups. We also examinedin vitroCa absorption by using everted sacs of the small intestine. Addition of PD to the serosal medium of the ileal sacs increased Ca absorption, but addition of GGH did not. These results suggest that the small intestine rather than the large intestine is responsible for the increase in Ca absorption in rats fed PD, and suggests that the mechanism for the increase by PD may be different from that by GGH.

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Colonic Handling of Calcium Appears To Occur Via Different Pathways in Mouse Models of Infants and Adults

Current Developments in Nutrition ◽

10.1093/cdn/nzab059_006 ◽

2021 ◽

Vol 5 (Supplement_2) ◽

pp. 1305-1305

Author(s):

Megan Beggs ◽

R Todd !Alexander

Keyword(s):

Gene Expression ◽

Molecular Mechanisms ◽

Epithelial Transport ◽

Engineering Research ◽

Ussing Chambers ◽

Funding Sources ◽

Critical Age ◽

Future Work

Abstract Objectives Calcium (Ca2+) is a vital micronutrient for many physiological functions with the greatest rate of accumulation occurring during the critical period of infancy. Previous work has demonstrated that molecular mechanisms of intestinal Ca2+ absorption across the small intestine are significantly different in animal models of infants and adults to permit greater absorption early in life. The colon contributes to overall Ca2+ balance in adults via transcellular, TRPV6 mediated and paracellular claudin-2 and -12 mediated pathways. Whether these same colonic pathways contribute to overall Ca2+ absorption in infants is not known. Here we aimed to investigate the molecular details of Ca2+ absorption across the large intestine in murine models of infancy relative to older mice. Methods Mice at 14 days (P14) were used as a model of suckling infants and mice at 2 months were employed to represent adult physiology. Wildtype and mutant mice with a non-functioning Trpv6 or deletions of Cldn2 or Cldn12 were used. Net 45Ca2+ flux (JCa) and Ca2+ permeability (PCa) were measured in Ussing chambers. Gene expression was determined by real-time PCR. Results JCa indicates net absorption across the colon at both P14 and 2 months. While gene expression of Trpv6 and S100g suggest greater cellular uptake of Ca2+ into colonocytes at P14, net JCa in vitro was not different than at 2 months. In contrast to previous work in mice at 2 months, TRPV6 does not mediate JCa at P14. PCa was 20% greater at P14 than 2 months, suggesting greater capacity for bidirectional diffusion of Ca2+ down an electrochemical gradient in younger mice. In contrast to previous work in mice at 2 months, claudin-2 and claudin-12 do not mediate PCa at P14 and, expression of Cldn2 and Cldn12 were significantly reduced in younger mice. Conclusions These results improve our understanding of intestinal Ca2+ handling during a critical age early in life. Future work is required to delineate molecular details under in vivo conditions of colonic Ca2+ transport in infants. Funding Sources This work was funded by grants from the Women and Children's Health Research Institute, which is supported by the Stollery Children's Hospital Foundation, and the National Sciences and Engineering Research Council to RTA, who is the Canada Research Chair in Renal Epithelial Transport Physiology.

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OCCULT MALABSORPTION CAUSING OSTEITIS FIBROSA CYSTICA

Acta Endocrinologica ◽

10.1530/acta.0.0400481 ◽

1962 ◽

Vol 40 (4) ◽

pp. 481-492

Author(s):

J. G. Devlin ◽

D. K. O'Donovan

Keyword(s):

Vitamin D ◽

Iron Absorption ◽

Calcium Absorption ◽

Calcium Balance ◽

Gluten Free ◽

Osteitis Fibrosa Cystica ◽

Mucosal Atrophy ◽

Cystic Changes ◽

Calcium Malabsorption ◽

Radiological Examinations

ABSTRACT A case is reported of intermittent hypercalcaemia, hypophosphataemia and severe skeletal rarefaction with cystic changes. An occult calcium malabsorption was found. Fat, triolein and iron absorption and radiological examinations were normal. There was gross intestinal mucosal atrophy. She was shown to be in a state of negative calcium balance and this was reversed by vitamin D. A gluten-free diet also improved calcium absorption. It is postulated that the patient had severe secondary hyperparathyroidism as the skeleton reverted to normal after six months of medical treatment.

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Calcium transport in turtle bladder

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1987.253.6.r917 ◽

1987 ◽

Vol 253 (6) ◽

pp. R917-R921

Author(s):

S. Sabatini ◽

N. A. Kurtzman

Keyword(s):

Calcium Transport ◽

Calcium Absorption ◽

Short Circuit ◽

Open Circuit ◽

Calcium Flux ◽

Bladder Epithelium ◽

Control Value ◽

Sodium Calcium ◽

Turtle Bladder ◽

Absorptive Flux

Unidirectional 45Ca fluxes were measured in the turtle bladder under open-circuit and short-circuit conditions. In the open-circuited state net calcium flux (JnetCa) was secretory (serosa to mucosa) and was 388.3 +/- 84.5 pmol.mg-1.h-1 (n = 20, P less than 0.001). Ouabain (5 X 10(-4) M) reversed JnetCa to an absorptive flux (serosal minus mucosal flux = -195.8 +/- 41.3 pmol.mg-1.h-1; n = 20, P less than 0.001). Amiloride (1 X 10(-5) M) reduced both fluxes such that JnetCa was not significantly different from zero. Removal of mucosal sodium caused net calcium absorption; removal of serosal sodium caused calcium secretion. When bladders were short circuited, JnetCa decreased to approximately one-third of control value but remained secretory (138.4 +/- 54.3 pmol.mg-1.h-1; n = 9, P less than 0.025). When ouabain was added under short-circuit conditions, JnetCa was similar in magnitude and direction to ouabain under open-circuited conditions (i.e., absorptive). Tissue 45Ca content was approximately equal to 30-fold lower when the isotope was placed in the mucosal bath, suggesting that the apical membrane is the resistance barrier to calcium transport. The results obtained in this study are best explained by postulating a Ca2+-ATPase on the serosa of the turtle bladder epithelium and a sodium-calcium antiporter on the mucosa. In this model, the energy for calcium movement would be supplied, in large part, by the Na+-K+-ATPase. By increasing cell sodium, ouabain would decrease the activity of the mucosal sodium-calcium exchanger (or reverse it), uncovering active calcium transport across the serosa.

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Stanniocalcin: a novel protein regulating calcium and phosphate transport across mammalian intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1998.274.1.g96 ◽

1998 ◽

Vol 274 (1) ◽

pp. G96-G102 ◽

Cited By ~ 22

Author(s):

Karen L. Madsen ◽

Michele M. Tavernini ◽

Christine Yachimec ◽

Donna L. Mendrick ◽

Pedro J. Alfonso ◽

...

Keyword(s):

Calcium Absorption ◽

Short Circuit ◽

Regulatory Protein ◽

Chinese Hamster ◽

Phosphate Transport ◽

Simultaneous Increase ◽

Rat Intestine ◽

Glycoprotein Hormone ◽

Phosphate Absorption ◽

Ussing Chambers

Stanniocalcin (STC) is an anti-hypercalcemic glycoprotein hormone previously identified in the corpuscles of Stannius in bony fish and recently in the human genome. This study undertook to express human STC in Chinese hamster ovary (CHO) cells and to determine its effects on calcium and phosphate absorption in swine and rat intestine. Unidirectional mucosal-to-serosal ( J m→s) and serosal-to-mucosal ( J s→m)45Ca and32P fluxes were measured in vitro in duodenal tissue in voltage-clamped Ussing chambers. Addition of STC (10–100 ng/ml) to the serosal surface of the duodenum resulted in a simultaneous increase in calcium J m→s and J s→mfluxes, with a subsequent reduction in net calcium absorption. This was coupled with an STC-stimulated increase in phosphate absorption. Intestinal conductance was increased at the highest dose of STC (100 ng/ml) in swine tissue. The addition of STC to the mucosal surface had no effect on calcium and phosphate fluxes. STC at doses of 10–1,000 ng/ml had no effect on short-circuit current in any region of the rat intestine. In conclusion, human recombinant STC decreases the absorption of calcium and stimulates the absorption of phosphate in both swine and rat duodenum. STC is a novel regulatory protein that regulates mammalian intestinal calcium and phosphate transport.

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Effect of pH on chloride absorption in the flounder intestine

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1988.255.2.g247 ◽

1988 ◽

Vol 255 (2) ◽

pp. G247-G252 ◽

Cited By ~ 1

Author(s):

A. N. Charney ◽

J. I. Scheide ◽

P. M. Ingrassia ◽

J. A. Zadunaisky

Keyword(s):

Small Intestine ◽

Short Circuit ◽

Ph Effect ◽

Short Circuit Current ◽

Bathing Solution ◽

Solution Ph ◽

Transport Pathway ◽

Ussing Chambers ◽

Chloride Absorption ◽

In Series

Chloride absorption in the small intestine of the winter flounder, Pseudopleuronectes americanus, is reported to be sensitive to ambient pH. We studied this sensitivity in isolated stripped intestinal mucosa mounted in modified Ussing chambers. Unidirectional 36Cl fluxes (JClm----s, JCls----m) were measured under short-circuited conditions in bathing solutions containing various combinations of HCO3- (0-20 mM), partial pressure of CO2 (0-36 mmHg), and pH (6.77-7.85). We found that JClm----s, net 36Cl flux (JClnet), and short-circuit current (Isc) increased and JCls----m decreased predominately in response to increases in bathing solution pH. There was a linear relationship between pH and both JClnet (r = 0.92, P less than 0.01) and Isc (r = 0.96, P less than 0.005) between pH 6.77 and 7.74. The pH effect was completely reversible, did not require either CO2 or HCO3-, and was not affected by the presence of mucosal barium at 1 mM. Mucosal bumetanide (0.1 mM) completely inhibited the pH effect. These data suggest that the process by which Cl- is absorbed in the flounder intestine is sensitive to pH. The data do not indicate whether pH affects Na+-K+-2Cl- cotransport or a Cl- transport pathway in series with this process. The direction of Cl- absorption in response to pH contrasts with inverse relation of pH and Cl- absorption in mammalian small intestine.

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Absence of a cAMP-mediated antiabsorptive effect in an undifferentiated jejunal epithelium

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1987.252.6.g776 ◽

1987 ◽

Vol 252 (6) ◽

pp. G776-G782

Author(s):

R. J. MacLeod ◽

J. R. Hamilton

Keyword(s):

Small Intestine ◽

Thymidine Kinase ◽

Jejunal Mucosa ◽

Ussing Chambers ◽

Luminal Membrane ◽

Viral Enteritis ◽

Transmissible Gastroenteritis ◽

Camp Levels ◽

Nacl Cotransport

In the relatively undifferentiated jejunal mucosa occurring in piglet viral enteritis, we measured the response of transepithelial Na+ and Cl- fluxes in vitro to raised intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels. At the acute 40-h stage of transmissible gastroenteritis (TGE), luminal membrane markers, sucrase and lactase, and a basolateral jejunal epithelial membrane marker Na+-K+-ATPase, were significantly decreased in activity, while a proliferative marker, thymidine kinase, was significantly enriched; these enzyme characteristics are typical of enterocytes isolated from crypts of other species. As expected, control piglet jejunum in short-circuited Ussing chambers after theophylline (10 mM) developed significant net secretory Na and Cl fluxes primarily due to significant antiabsorptive effects (delta JNa m----s = 3.48 +/- 0.52, delta JCl m----s = 2.59 +/- 0.28). Furosemide (10(-4) M), an inhibitor of electroneutral NaCl cotransport, produced antiabsorptive effects (delta JNa m----s = 2.53 +/- 0.31, delta JCl m----s = 2.58 +/- 0.28) in control jejunum that were not significantly different from those seen in response to theophylline. TGE jejunum, however, responded to theophylline not by an antiabsorptive effect but by significant electrogenic Cl- secretion (delta JCl s----m = 1.59 +/- 0.48); furosemide had no effect on ion fluxes in TGE tissue. Control and TGE jejunal mucosal homogenates did not differ in their basal or theophylline-stimulated levels of cAMP. We conclude that the relatively undifferentiated small intestine occurring in acute TGE does not generate either a cAMP-mediated antiabsorptive effect or a furosemide-mediated antiabsorptive effect.(ABSTRACT TRUNCATED AT 250 WORDS)

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Complete Proceedings - Single PDF Download

Coastal Engineering Proceedings ◽

10.9753/icce.v15.all ◽

1976 ◽

Vol 1 (15) ◽

Author(s):

ASCE ASCE

Keyword(s):

Research Council ◽

Coastal Engineering ◽

The State ◽

Engineering Research ◽

Engineering Conference

Proceedings of the Fifteenth Coastal Engineering Conference, Honolulu, HI, July 11-17, 1976 Sponsored by the State of Hawaii, University of Hawaii, ASCE through its Coastal Engineering Research Council, and American Shore and Beach Preservation Association.

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